The invention relates to the technical field of vehicle steering wheels.
The invention concerns more particularly dynamometric steering wheels.
Steering wheel means a manually controlled device connected to the front wheels and used by the driver to direct the vehicle.
Field of the Invention
Conventionally, the steering wheel is connected to the front wheels by a steering column, that is to say a tubular element fixed to the bodywork, under the dashboard, which guides and supports the transmission shaft connected to the steering wheel.
This steering column is associated with a steering box, for example a rack, converting the circular movement of the steering wheel into an angular movement of the steering rods which cause the wheels to steer.
The invention also concerns the steering wheels integrated into the steering device in which the wheels are not connected by a series of mechanical components with the steering wheel.
Steering wheels conventionally consist of a toric rim connected by at least one connecting arm to a hub cooperating with the steering shaft.
Reference can be made, for example, to the following documents: EP-726 185, EP-691 254, EP-504 963, EP-412 605, EP-465 296, EP-390 001, EP-368 386, EP-329 542, EP-309 316, FR-2 679 859, FR-2 674 207, FR-2 662 132, FR-2 664 223, FR-2 620 996.
Steering wheels frequently serve as a support for comfort or safety equipment, without any functional link with the steering column.
Such is the case, for example, with steering columns forming a support for an inflatable airbag.
Inflatable airbag means here a passive retaining device formed by a flexible casing inflated in the event of impact by an explosive system, so as to fill a space in front of the driver.
Steering wheels with an integral airbag conventionally comprise a body formed by a rim and arms connecting to a hollow hub in which a central airbag support hub is housed.
Reference can be made, for example, to the following documents: EP-728 652, EP-788 935, FR-2 718 699, FR-2 716 857, FR-2 709 461.
Accessories other than airbags are sometimes integrated into or housed in the hollow of steering wheels: horns, indicator lights etc, these accessories having no functional link with the steering wheel and not fundamentally modifying the structure thereof.
Reference can be made, for example, to the following documents: EP-744 329, EP-668 205, EP-647 540, WO-96/255 28, WO-94/112 12 30, FR-2 681 570, FR-2 633 239, FR-2 633 237.
The invention relates to an instrumented steering wheel structure, the sensor 25 integrated into or attached to the structure or frame of the steering wheel being a torque sensor or torque meter.
To this end, the invention relates, according to a first aspect, to a steering wheel frame, notably for a motor vehicle, having
ergonomic means for gripping the steering wheel to control the rotation of a steering shaft;
means of mounting the steering wheel frame on the said steering shaft comprising a means of measuring the stresses applied to the steering shaft by the manoeuvring of the steering wheel.
The means of measuring the stresses applied to the steering shaft by the manoeuvring of the steering wheel comprise at least one torque sensor.
In one embodiment, the steering shaft is a component of a steering column mechanically connecting the wheels to the steering wheel.
In another embodiment, the steering shaft is a principal shaft of a decoupled steering device.
According to one characteristic, the means of measuring the stresses applied to the steering shaft by the manoeuvring of the steering wheel is a small-movement sensor.
The frame comprises an annular rim and at least one arm connecting the rim to the stress measuring means.
The frame comprises at least one ergonomic grip for gripping the steering wheel.
The grip is fixed by clamping members to the periphery of the steering wheel or to one of the arms of the steering wheel.
The grip supports means of controlling components of the vehicle.
The rim comprises at least two substantially complementary tubes shaped in a portion of a ring, each tube comprising a portion of the rim and at least one-radially folded end part forming at least part of an arm of the frame.
The radial arms are connected to the rim, the end part of one or of each arm being inserted in a corresponding slot in the rim, in one embodiment.
In another embodiment, the radial arm or arms are made from pressed sheet metal, the end part of one or each arm being coiled on the rim and welded thereto.
The frame includes means of connecting an inflatable airbag device.
In a variant, the frame has means of connection either with an insert encased in padding, an inflatable airbag mechanism being encased in the padding, or with a plate connecting the steering wheel gripping means to the steering shaft.
The torque sensor has:
a first movable external ring;
a second external ring, substantially unstressed, placed at a distance from the movable external ring;
an internal ring fixed with respect to rotation to the steering shaft to which the torque to be measured is applied, the movable external ring being able to be rigidly fixed to the steering wheel frame, the movable external ring being connected to the internal ring by at least one elastically deformable means;
the external ring, substantially unstressed, being connected to the internal ring by at least one substantially unstressed means;
the sensor comprising means of measuring small relative movements of the movable external ring with respect to the substantially unstressed external ring when a torque is applied to the steering shaft via the steering wheel frame.
Other objects and advantages of the invention will emerge during the following description of embodiments, a description which will be given with reference to the accompanying drawings, in which: